Preparation of carbonate salts of calcium and magnesium



Patented Nov. 9, 1948 EREPARAHJIDM E-"@ARBONATE SALTS OF *EALQIUMLAAND MAGNESIUM: Walter McGcorge, Kingston Hill, and Francis Highland Milner, Twickenlia n; England.

No. nrawin a Application Julie 23,..1940, it S enialfi No; 347,037.; ,ImGrea-t BritainAugust25 1il39' 51' Claim. (01. ism-m so-called stomach powders nowt on the market; usually consist of sodium bicarbonate,

calcium carbonate, basic magnesium carbonate and-bismuth carbonate, the individual compo nents being prepared separately and thereafter blended in the required proportions. The initial preparation should b'e such as to give a small particle size and the blending should it be sufficientlythorough to resultin a substantially uniform mixture. These requirements give rise to certainpractical difficulties,.particularly s grind-r ing is. not always desirable and in any case cal ciurn carbonate exhibits a tendency to agglomeratevwhich impairs the blending.

The. object of thepresent invention is to provi de avsuitable stomach powder base containing calcium and magnesium incarbonate form andl corporaling the in the proportions required in the final stomach powder which is produced: from the base by indesired further component, or components. p n I" The discovery on which the present invention is based. is that by theadmixture ofan aqueous solution of soluble salts of calcium and magnesiurn', and an aqueous solution of vwater-soluble carbonate salt such as sodium carbonate, it. is possible by proper control of the conditions to obtain a finely divided precipitate containing;

calcium and magnesium in carbonate form and in very intimate mixture.

The initial result. of the reactionbetween the two solutions is a gelatinous. precipitate whicht is converted, by the action of heat into the! deslred finely dividedform. If the reaction is car ried out at a suitably raised temperature the" gelatinous product isconverted continuously during the reaction, whereas if the reaction i'slcarriedput attroom temperature the conversion of the entire gelatinous productha st to beeffectedi by heating subsequent to the reaction.

The invention thus resides essentially in a process wherein a water-soluble carbonate saltin aqueous solution is'mixed with an aqueous solution of water-soluble salts of calcium and magnesium under conditions resulting in the co-precipn tation of both calcium and magnesium in can bonate form with less than occludedsodium and. in a finely divided and. intimately mixed. cone dition. t

Theadmixtureis efi'ected by causingiboth soln. tions to pass: at corresponding rates.- through at common pipe in which. the reaction occurs] If the solutions are not heated before. the reaction,

the conversion ofthe precipitate into thedesired;

form is effected byheating. the. eiiluentt fonfthe;

t 25 appropriate? period. Ii" desiredl agitating; means mayibe provided at. the; inlet to the common pipe; t'oensure intimate int'ermi'ngling, of the two solutions.

In order to produce: by the process, according to the invention a stomach powder base of acomposition equivalent to a base obtained by mixing calcium carbonate and basic magnesium carbonateasobtainedby separate precipitation from solution by sodium carbonate, a. solution of so dium carbonate containing not more than parts by weight of' sodium carbonate in 230 parts bytweightof'water'and a solution oficalciumchloride and magnesium: chloride containing calcium andinagnesium in the proportions. desired inthe product and atthe rafte' of not more than I00 parts byfweight of" the two chlorides in parts bywei'ght of water, the quantity of the, sodium carbonate solution being in excess of tlietheoretical quantity required for precipitating all .the calcium and magnesium, and n the solutions being admixed, whereaft'er' the mixture allowed. to

digestfor aperiod not less than the time taken for the gelatinous precipitate-rimmed to granulate or crystallise into a precipitate which will settle rapidly on standing: The precipitate is then washed and dried. i The amount of sodium" carbonate' solution employed may beup tm 25% in excess of the" theoretical quantity; but" preferably: the eXcessamount is no greater than is fo'und ne'cessary in practice for thecomp'lete' precipitation of the-calcium and in'agnesiurn" (about 5%);

The washing i's preferably effected Eyre-sus pending-- theprecipitate in warm watenand-rafiltering, theatreat ment' being repeated at leasttwice before-the precipitate is drie'di Ian-roun parently present as afi-complex carbonatezprob that analysis of the precipitate aft'encarefulwashing: still shows a; sodium content, a property whicl'r is common to: all magnesium carbonates obtained by precipitation with sodium carbonate: In. general, dilution of the reacting solutions reduces the occluded sodiumand provided the con ditions stipulated above are maintained; the so "dium; contentremainsa less than 1 0 and is not detrimental: Moreover; the sodium which is ap ably chemically bound to the magnesium car bonate, cannot. be tasted. when the powderistaken orally, Whenit is desired to, obtain a low sodium. content, the carbonate-solution isadded to the chloride:solutiomastaddina in therreverse order: is fo'und. to give; an. appreciably greater amount of occluded sodium in the product;

In order that the: duration oi theireaction for.

an economic yield should be commercially practicable, the sodium carbonate solution should contain not less than 100 parts by weight of sodium carbonate in 4,000 parts of water and the mixed chloride solution not less than 100 parts by weight of the two chlorides in 4,000 partsof Water. The precipitate obtained within these concentration limits has a bulk density comparable with that obtained by blending equal parts by weight of calcium carbonate and basic magnesium carbonate (heavy).

The aqueous solution of soluble salts of calcium and magnesium may be prepared from the individual soluble salts in question, or alternatively the starting material employed may be a naturally occurring material containing v both magnesium and calcium in carbonate form. Examples of such material are dolomite, i. e. the double carbonate of magnesium and calcium containing equivalent molecular proportions of magnesium and calcium, and magnesian limestone which contains both magnesium and calcium vcarbonatesbut with a preponderance of calcium carbonate. A solution containing salts of both elements is prepared from this starting material by means of a suitable acid. such as hydrochloric acid.

If the proportions of magnesiumand calcium in the raw material differ from the desired proportions in the final product, the proportions can be adjusted by the addition of magnesite or Example 1 A solution containing 46.3 parts of sodium car bonate in 110 parts of water at 100 C., is added gradually during a period of ;minutes to a solution containing 22.6 parts of calcium chloride and 20.2 parts of magnesium chloride in 88'parts of water at 100 C., the mixture being mechanically stirred. The mixed solutions are allowed to digest at 100 C. for 20 minutes. The precipitate is then removed by filtration. It is then re-suspended'in 300 parts of warm water and refiltered. The re-suspension and filtration are re-v peated twice and the precipitate is finally dried at 100-120 C.

Analysis of a precipitate obtained in accordance with Example 1 showed a sodium content of 0.84%. i l

Repeating the experiment under otherwise equal conditions using the original solutions diluted to 2, 4 and 10 times their original weights with water and an identical series of experiments in which the chloride solution was added to the carbonate solution gave the following sodium contents:

Concentration 1 A 34 Mo I Per cent Sodium content (Carbonate to chloride) 0. 84 0.28 0. 21 0. 16 Per cent Sodium content (chloride to carbonate) 4.47 0.82 0.49 0.31

.-C..for 5 minutes.

tained at 100 C. throughout.- washed three times and dried. The sodium con} Example 2 A solution of 154 grms. of calcium chloride (72.3% CaClz) and 210 grms. of magnesium chloride hexahydrate in 180 grms. water is added gradually during a period of 5 minutes at 100 C. to 270 grms. of sodium carbonate in 620 grms. water. The mixture is allowed to digest at 100 The product is separated, washed three times by re-suspension in a vol- .ume of tap water equal to the volume of mother liquor, and thereafter dried at 100420 C. The

sodium content is found to be 3.99%.

Example 3 A solution of 154 grms. of calcium chloride (72.3% CaClz) and 210 grms. of magnesium chloride hexahydrate dissolved in 180 grms. of water is added at a uniform rate in sixty minutes to 270 grms. of sodium carbonate in 620 grms. water. The mixture is then allowed to digest for sixtyiminutes. The temperature of the solutions is maintained at 100 C. throughout. The prodnot is washed three times and dried as before. The sodium content is found to be 8.96%.

Example 4 A solution of 154 grms. of calcium chloride 2 (72.3% CaClz) and 210 grms. of magnesium chloride hexahydrate dissolved in 180 grms. water is added in twenty minutes to a solution of 270 grms. of sodium carbonate in 620 grms. water. The mixture is allowed to digest for twenty min utes. The temperature of the solutions is main- The product is tent is found to be 9.30%.

. Example 5 A solution of 46.3 grms. of sodium carbonate in 1517 grms. water is added in twenty minutes to a solution containing 20.2 grms. of magnesium chloride and 22.6 grms. of calcium chloride in 1267 grms. Water. The mixture is allowed to digest for twenty minutes and the temperature is maintained at 0. throughout. The product is washed three times and dried. The sodium con-.

tent is found to be 0.16%.

Example 6 120.5 parts of calcium chloride hexahydrate and 116 parts of magnesium chloride hexahydrate are dissolved inwater to 1,000 parts and 125 parts of sodium carbonate anhydrous is dissolved in water i to 1,000 parts. Thetwo solutions are led or pumped into a common pipe at equal rates and.

the eiiluent is heated to C. for half an hour, after which the precipitate is removed by filtration and washed as described examples.

In these examples it is assumed that pharmaceutical pure starting materials are employed. If however commercial grades of the raw materials are utilised, a preliminary purification of the individual solutions may be carried out by adding a small quantity of the carbonate solution to the. chloride solution, preferably with vigorous fagitation in the cold, and by similar addition of a small quantity of the chloride solution to the car- A gelatinous precipitate is obbonate solution. tained, which can be removed by filtration or if desired by coagulation or the precipitate by heating followed by filtration. Any iron, arsenic, lead. or the like present in the raw materials is removed in the precipitate and the filtrates are in previous utilised for the production of the carbonate salts by the process according to the present invention.

Example 7 'is added to the bulk of the sodium carbonate solution and 19 mls. of carbonate solution is added to the bulk of the dolomite solution. The two mixed solutions are each heated to about C. when the precipitate resulting from the admixture of the small proportion of the other solution coagulates. The two solutions are each filtered and the filtrates are caused to interact ,under the conditions already described. The reaction is brought to a temperature of C. and is maintained at this temperature until coagulation of a the precipitate takes place, after which the, precipitate is removed by filtration or decantation and is washed with fresh water several times. Finally it is separated from the wash liquor and dried.

The cross precipitation serves to remove the impurities, viz: arsenic, lead, iron, and aluminum, present in the starting materials. To ensure the complete removal of iron from the dolomite solution, the precipitation of impurities therefrom by the addition of a small quantity of the sodium carbonate solution can be carried out in the presence of a soluble oxidising agent which does not form a precipitate with calcium and/or magnesium, e. g. hydrogen peroxide. purification can be carried out with larger or smaller quantities of the solutions but the quantities of solution and the conditions of reaction have to be adjusted in each case so as to give the desired removal of impurities. When this purification is effected the final precipitate resulting from the interaction of the purified solutions is pure white in colour and is found to be an intimate mixture of magnesium and calcium carbonates in extremely finely divided form.

When using a material such as magnesian limestone, which has a smaller magnesium content than dolomite, the adjustment of the magnesium content can be effected by adding the ap- An equivalent.

propriate amount of magnesite to the magnesian limestone or by adding magnesium chloride to the solution obtained with hydrochloric acid. The adjustment of the calcium content can be carried out in a precisely analogous manner.

As an example of the production of a stomach powder from the stomach powder base produced in accordance with thefforegoingythe following proportions are given:

8 parts by weight of the base.

2 parts by weight of sodium bicarbonate in a finely divided state, preferably produced in accordance with our co-pendin-g application No. 347,- 038, now Patent No, 2,373,147.

1 part by weight of bismuth carbonate in a finel divided state. i

The components are mixed or blended mechanically to give a substantially uniform mixture.

We claim:

A process for the preparation of a stomach powder base comprising mixing an aqueous solution of sodium carbonate containin-gsodium carbonate in the ratio of parts by weight of sodium carbonate to 230 to 4000 parts by weight of water, with a solution of calcium chloride and magnesium chloride containing calcium and magnesium in substantially equimolecular proportions desired in the product and at the ratio of 100 parts by weight of the two chlorides in to 4000 parts by weight of water by flowing the sodium carbonate solution and the calcium chloride and mag:

nesium chloride solution together into a common flow zone whereby the two solutions are intermingled and caused to interact resulting in the coprecipitation of bothcalcium and magnesium.

in carbonate form and in a finely dividedand intimately mixed condition, the quantity of the sodium carbonate solution being inexcess of the theoretical quantity required for precipitating the calcium and magnesium.

WALTER MCGEORGE. FRANCIS H.

REFERENCES CITED The following references are of record file of this patent:

Hunt, American Journal of Science and Arts, Second Series, vol. 42 (1866), pages 54 and 66..

Gutman, Modern Drug (Encyclopedia), 1934, page 347.

in the Mellor, Comprehensive Treatise on Inorganic and Theoretical Chemistry, vol. IV, pages 372- 375. 

